To the best of our knowledge, the present study was the first to examine the associations between trait impulsivity, choice impulsivity, and binge-eating behavior in general samples. The results supported our hypotheses that individuals with binge eating disorder (BED) might have elevated impulsive personality traits than the healthy controls. Specifically, the BED subjects showed higher levels of trait impulsivity on the BIS-11 (i.e., Attentional Impulsiveness, Motor Impulsiveness) and UPPSP (i.e., Negative Urgency, Lack of Perseverance, Positive Urgency). However, the BED group had a normal level of choice impulsivity both on the DDT and the PDT (except on the PDT Part A), compared with the healthy controls. Significant positive correlations were found between BES scores and most impulsivity scores, including BIS Attentional Impulsiveness, Motor Impulsiveness, Non-planning Impulsiveness, UPPSP Negative Urgency, Lack of Perseverance, and Positive Urgency. More importantly, regression models showed that only Negative Urgency positively predicted binge eating as an important risk factor. These findings suggested that different impulsivity facets were separately associated with BED, and certain trait impulsivity (i.e., Negative Urgency) might be considered a hallmark for BED in young adults.
Increased impulsivity has been proposed as a phenotype for addictive disorders as well as within the clinical obesity spectrum , and it might also increase the risk for BED. However, few studies have focused on the relationship between impulsivity and binge eating in non-treatment-seeking individuals with normal weight. The current study investigated the associations of trait impulsivity, choice impulsivity, and binge-eating behavior in common populations (i.e., young adult college students). The data showed that individuals with BED had elevated scores on measurements of trait impulsivity (i.e., Attentional Impulsiveness, Motor Impulsiveness, Negative Urgency, Lack of Perseverance, and Positive Urgency), consistent with previous reports on BED[34, 56, 57, 58, 59] and addictive disorders[60, 61, 62].
Furthermore, positive correlations were found between the BES score and these impulsivity scores (Table 2). However, only Negative Urgency displayed the main effect as a positive predictor of binge-eating behavior in the regression models (Tables 3, 4). This finding suggested that elevated Negative Urgency might represent a preclinical susceptibility marker for binge eating disorder, although longitudinal studies are needed to clarify whether Negative Urgency precedes the onset of binge eating or as a consequence of BED. Nevertheless, our first direct evidence in non-treatment-seeking populations showed that specific trait of impulsivity (i.e., Negative Urgency) was overtly enhanced in binge-eating behavior [63, 64, 65]. Negative urgency reflects a tendency to act impulsively under the condition of extreme negative emotions . Individuals with elevated Negative Urgency seemed more likely to be involved into binge eating in order to deal with negative emotions, and as a result, their binge-eating behaviors would be reinforced or deteriorated . Our results increased new knowledge to the current literature that Negative Urgency could play a key role in BED even among non-clinical samples, as a potential susceptible hallmark of binge-eating behaviors.
On the other side, the BED group did not show an aberrant pattern of choice impulsivity. The data revealed that the BED subjects performed similarly with the healthy controls on the Delay Discounting Test (DDT) and the Probability Discounting Test (PDT), though the BED group displayed a lower probability-discounting degree on the PDT Part A (i.e., $20 VS $80) with a low to medium effect size (Cohen’ s d = 0.370). Moreover, the DDT k value and PDT h values were not significantly associated with or predictive of binge eating (Tables 2–4). Recent studies found that obese females with BED had higher discounting degrees of delayed reward , and drug addicts displayed a lower risk aversion compared to matched controls [69, 70]. Among clinical samples of BED and obesity without BED, reduced reward processing in the striatal and amygdala regions indicated motivational hypo-function to non-food rewards [71, 72]. However, a longitudinal study showed that the ventromedial prefrontal cortex (vmPFC) activation did not display a significant predictive effect on binge-eating severity in adolescent girls . Therefore, further studies should be conducted to investigate the processes of delay gratification and risk aversion in both clinical and non-clinical samples of BED.
Several limitations should be noted in the current study. Firstly, this study was a cross-sectional design in nature, and thus could not draw a causal conclusion between impulsivity and BED. Moreover, the samples consisted of young college students and our results could not be generalized to clinical samples with serious binge-eating problems. Future research should investigate the relationship of trait impulsivity (e.g., Negative Urgency) with binge-eating behaviors in more severe clinical patients. Thirdly, given that our study mainly focused on some aspects of impulsivity (i.e., trait impulsivity and choice impulsivity) measured by self-report scales, these findings should be interpreted more carefully because of the possible subjective bias, and other facets of impulsivity should be further investigated using more objective tasks.
In despite of these limitations, the present study firstly looked into the associations between various aspects of impulsivity and binge-eating behavior in non-clinical samples of BED, using a case-control design. Our results indicated that Attentional Impulsiveness, Motor Impulsiveness, Negative Urgency, Lack of Perseverance, and Positive Urgency were elevated in BED and especially, Negative Urgency was the only risk factor positively predicting BED. These findings suggested that typical facets of trait impulsivity, which have been recognized in addictive disorders, were associated with BED in young adults, whereas choice impulsivity was not aberrantly seen in BED.